Persistent pulmonary hypertension of the newborn is a serious disorder that occurs when a baby fails to adapt to the circulatory transition as they breathe through their lungs after birth.
Circulatory adaptation occurs minutes after birth as the baby transitions from receiving oxygen from the placenta through the umbilical cord to breathing independently.
When this does not happen, the blood flow from the heart to the lungs becomes insufficient. In turn, not enough oxygen reaches the bloodstream to supply the brain and the rest of the body.
This article discusses pulmonary hypertension in newborns, its signs and symptoms, risks, and complications.
Persistent pulmonary hypertension of the newborn (PPHN) occurs when conditions like low oxygen levels or breathing problems prevent natural circulatory changes.
During pregnancy, babies get their oxygen from the placenta, an organ in the womb supplying oxygen and nutrients from the mother’s blood to the baby through the umbilical cord.
Upon taking their first breath, the blood vessels of the newborn’s lungs widen or dilate. This dilation should cause a rapid increase in blood flow to the lungs, closing the fetal pathway and causing circulation changes. This process causes blood to travel through the lungs to get oxygen before it flows to the rest of the body.
In PPHN, pulmonary arteries do not widen enough, limiting the blood flow to the lungs and causing the pressure in the lungs’ blood vessels to build up. This condition also results in the persistence of the old blood pathway where blood flows from the right to the left atrium, which bypasses the lungs.
How common is it?
PPHN happens in 2 in every 1,000 live births. It occurs more in full-term babies, those born past their due dates, and those born after 42 weeks. Doctors are also diagnosing PPHH
Despite advances in care, it is still one of the leading causes of morbidity and death among babies, reaching a 4–33% mortality rate.
Doctors can identify symptoms of PHNN at birth or within the first hours of birth. These include:
- rapid breathing and shortness of breath
- respiratory distress, including nose-flaring, grunting, or moaning
- retractions or pulling in of the skin under the ribs when breathing hard and fast
- cyanosis or pale blue color of the skin, lips, skin, hands, and feet
- low blood oxygen levels, even when doctors provide 100% oxygen
- hands and feet are cool to the touch
- low blood pressure
- low APGAR scores
- heart murmur, or the presence of an extra or an abnormal heartbeat
- weak pulses
Lack of oxygen to the brain may cause long-term health problems, including:
- developmental delays
- hearing problems such as deafness
- functional disabilities, or decreased ability to perform physical activities
PPHN occurs when the blood vessels in the lungs fail to dilate. Conditions that prevent the vessels from dilating include:
- severe distress during delivery, including meconium aspiration syndrome
- infections, such as pneumonia and sepsis in the newborn
- problems with the placenta, such as placenta previa and placenta abruption
- congenital abnormalities, including:
- diaphragmatic hernia
- blocked heart valves
- underdeveloped lungs
- collapsed lung
- taking certain drugs during pregnancy, including:
- large doses of aspirin
Babies are at a higher risk of PPHN if they have:
- aspirated meconium — breathed in their bowel movements before birth
- asphyxia — having too little oxygen before or during birth
- infection in their blood, such as sepsis or lungs, such as pneumonia
- abnormal lung or heart development
- born to a mother with diabetes
- born large for gestational age
A pediatrician will check for the baby’s health status and delivery history. They will then do the following tests to determine if the newborn has PPHN:
- Monitoring oxygen saturation levels: This measures the oxygen saturation level in different body parts to see whether the newborn’s tissues are receiving enough oxygen.
- Echocardiogram: This test sends sound waves to generate an image of the heart and blood vessels. It is the most reliable test to establish a diagnosis of PPHN and look for structural heart diseases.
- X-ray: Checks for underlying lung or heart disease, including meconium aspiration syndrome and pneumonia. It also identifies whether the heart is too large.
- Blood tests:
- arterial blood gas levels measure the level of oxygen and carbon dioxide in the blood
- complete blood count with differential look for signs of infection and monitors for conditions such as polycythemia and hyperviscosity syndrome, which can lead to or worsen PPHN
- glucose and serum electrolyte levels
The treatment of PPHN depends on the underlying cause, severity, symptoms, and general health. The main goals of treatment are to:
- increase the oxygen levels in the newborn’s blood
- maintain appropriate blood pressure
- open the blood vessels in the lungs to improve blood flow
Doctors will supply newborns with oxygen through various means:
- Supplemental oxygen: Medical professionals send oxygen through a small tube with prongs placed in the nostrils, a plastic hood, or a mask.
- Endotracheal tube: Doctors place a tube through the windpipe, known as the trachea, to provide oxygen.
- Ventilator or mechanical breathing machine: A breathing tube connected to a ventilator passes through the windpipe. The machine breathes for the newborn until they can do it by themselves.
- Continuous positive air pressure: This is a noninvasive machine that gently delivers oxygen into the lungs
- High-frequency oscillation ventilation: This machine rapidly delivers very short bursts of oxygen through a breathing tube. This machine aims to improve oxygen levels when others are not effective.
Nitric oxide is the only drug approved for widening or dilating the pulmonary blood vessels used specifically for the treatment of PPHN. Doctors administer nitric oxide through the breathing machine to reach the lungs directly.
Different medications can help treat PPHN, depending on the underlying cause and related symptoms. Doctors usually administer these medications through an IV line directly into the vein. These may include:
- Blood pressure medication: These keep the newborn’s blood pressure stable.
- Sedatives: These drugs help keep the baby calm and help the machines that give them oxygen work better.
- Surfactants: Surfactants help the lungs work better, allowing them to use oxygen and remove carbon dioxide. Doctors give these through a breathing tube to premature infants and full-term babies with parenchymal lung disease.
- Antibiotics: Doctors prescribe these to treat infections.
- Inotropes: These medicines go directly into the bloodstream to keep the newborn’s blood pressure high, inducing the heart to pump more blood into the lungs.
Doctors will also check the following for a newborn:
- maintain body temperature
- check glucose and electrolyte levels
- correct metabolic imbalances and blood abnormalities
- provide nutritional support
- assess blood pressure
- monitor oxygen levels
Extracorporeal membrane oxygenation (ECMO)
Doctors use ECMO when all the other approaches fail to increase the newborn’s oxygen saturation levels. It takes over the functions of the lungs and the heart.
They drain blood from the newborn into an artificial lung, which places oxygen and removes carbon dioxide from the newborn’s blood. Doctors then pump the blood back to the newborn.
PPHN is a severe condition. It occurs when the newborn fails to transition from fetal circulation to the expected circulation, which involves the heart pumping blood to the lungs.
Different factors may cause this, but it often occurs in babies with a difficult birth and full-term and babies born past their due dates.
The goal of treatment is to increase the oxygen levels in the blood. Long-term health problems and complications can occur if the baby does not get enough oxygen delivered to the brain and other organs.